(1) Field of the Invention
The present invention pertains to a deep well submersible pump, and in particular a deep well submersible pump construction that employs fewer pump stages than prior art deep well pumps, resulting in reduced materials cost and easier assembly of the pump.
(2) Description of the Related Art
Deep well submersible pumps are employed in pumping liquids such as water from deep well holes having relatively small bore diameters. Pumps of this type are specially built for their environment and typically include a centrifugal pump having a series of vertically stacked radial impellers driven by an electric motor. The entire pump construction is dimensioned to enable the pump to be lowered into a well and suspended in the liquid at the bottom of the well by a series of interconnected downpipes. One example of a current design of a deep well pump consists of twenty stages, i.e. twenty impellers, and a motor driving the impeller stages at 3,600 RPM.
This pump assembly measures 36 inches in length and 3.5 inches in diameter. Some pump designs have also employed electric motors that operate at greater speeds, for example 12,000 RPM, to reduce the number of impeller stages while obtaining the same performance. Pumps of this type typically employ three or four stages or impellers to obtain the desired performance. Both the impellers and the liquid return channels of these prior art pumps are of the radial type.
Deep well submersible pumps have limited diameter dimensions so that they can be operated in well bores of only 4-5 inches in diameter. The pump is mounted in the bottom downpipes of a series of downpipes suspending the pump in the well bore with the electric motor of the pump being oriented vertically. The impellers of the pump are mounted on the vertically oriented shaft of the motor in vertically spaced relative positions. On rotation of the motor shaft, the impellers draw liquid into the pump housing and force or push the liquid centrifugally outward and upward through the impeller and return channel stages, thereby lifting the liquid through the pump housing and the series of downpipes to the surface opening of the well.
Due to the multiple stages of impellers and return channels employed in current designs of deep well submersible pumps, considerable time and effort is needed to assemble the pumps. In addition, increasing the impeller and return channel stages of a pump increases its weight. The increased weight of a pump often requires the use of metal downpipes with increased side wall thicknesses to lower the pumps and suspend the pumps in the liquid at the bottom of the well, thereby further adding to the overall weight of the pump and its downpipes. The increased number of pump stages and the increased size of the pump downpipes also result in increasing the cost of the pump assembly. Furthermore, in order to obtain different performance levels from a pump assembly, it is often necessary to assemble different numbers of stages with different numbers of impellers and return channels or use a different family of impellers and return channels.
A more simplified pump construction that reduces the number of component parts of the pump and thereby reduces the weight of the pump and yet is capable of operating in a range of desired performance levels would overcome the disadvantages associated with prior art deep well submersible pumps.
The deep well submersible pump of the invention overcomes disadvantages associated with prior art deep well submersible pumps by providing a single stage 12,000 or higher RPM pump of simplified construction. The pump is designed to use only a single stage and is basically comprised of a radial impeller and an axial diffuser/deswirler in the pump housing.
The pump housing is comprised of a cylindrical side wall with axially opposite ends surrounding an interior volume of the housing. An inlet end of the side wall is covered by an inlet cap having a centered inlet opening and the axially opposite outward end of the side wall is covered by an outlet cap having a centered outlet opening.
An electric motor is contained in the side wall with a shaft of the motor projecting axially toward the inlet opening of the inlet cap. The exterior surface of the motor casing is spaced, radially inward from the side wall interior surface, defining an open annular channel between the casing exterior surface and the side wall interior surface.
A tubular cowling is mounted on the motor casing adjacent the inlet cap. The cowling has an annular shoulder surface adjacent the inlet cap. The tubular cowling has an exterior surface that, together with the interior surface of the inlet cap and the interior surface of the side wall, defines an annular flow path that extends radially away from the inlet opening of the inlet cap and then curves and extends axially between the cowling exterior surface and the inlet cap and side wall interior surfaces. As the flow path extends axially between the cowling exterior surface and the side wall interior surface, the radial spacing between these two surfaces increases.
In addition, deswirl or a reduction in the swirl of the flow is provided by a plurality of circumferentially spaced blades between the cowling exterior surface and the side wall interior surface. Each blade has opposite inlet and outlet ends that are spaced axially from each other. The inlet ends of the blades are oriented in generally circumferential directions relative to the cowling and side wall and the trailing ends of the blades are oriented in generally axial directions relative to the cowling and side wall.
The interior surface of the inlet cap has a peripheral portion that extends radially outwardly away from the inlet opening of the cap and then curves continuously toward the side wall and extends axially and merges as a continuous surface with the interior surface of the side wall. An annular shoulder is formed in the interior surface radially inward of the peripheral portion of the cap interior surface and axially opposite the cowling annular shoulder. The inlet cap inlet opening is surrounded by a flat, annular rim surface on the cap interior surface.
The impeller of the pump is mounted on the motor shaft and is comprised of an axially inner disk and an axially outer disk that are spaced from each other by a plurality of impeller vanes between the disks. The axially outer disk has a center hole surrounded by a flat, annular rim surface. The flat, annular rim surface mates in sliding engagement with the flat, annular rim surface of the inlet cap inlet opening, thereby providing a sealing engagement between the two rim surfaces. The axially outer disk also has a flat, annular peripheral edge surface that opposes the annular shoulder on the inlet cap interior surface, thereby providing an additional seal between the outer disk and the inlet cap. The axially inner disk has a flat, annular peripheral edge surface that radially opposes the annular shoulder surface of the cowling and thereby provides a sliding seal between the inner disk and the cowling. The plurality of impeller vanes are circumferentially spaced around the axially spaced inner and outer disks. Each blade has an inner end adjacent the outer disk center hole and a radially opposite outer end adjacent the annular peripheral edge surfaces of the inner and outer disks.
On operation of the pump motor, the impeller is rotated drawing liquid from the well vertically upward through the inlet cap inlet opening and the outer disk center hole into the spacing between the impeller inner and outer disks. The impeller vanes then push or force the liquid radially outward toward the flow path defined between the cowling exterior surface and the interior surfaces of the inlet cap and side wall. The curved surface of the inlet cap interior surface peripheral portion turns the flow of liquid axially and directs the liquid through the blades of the axial diffuser/deswirler which direct the liquid flow through the annular channel between the motor casing exterior surface and the side wall interior surface. The liquid continues through the annular channel to the outlet end cap where it exists the pump interior volume through the outlet cap outlet opening.
The simplified construction of the deep well submersible pump of the invention reduces assembly time and the costs associated therewith, and reduces material costs significantly by reducing the number of stages of the pump. Using higher speeds allows the use of smaller motors which also significantly reduces the weight of the pump, enabling the pump to be used with plastic downpipes suspending the pump in the well which further reduces the overall weight of the pump assembly. The construction of the pump also enables the use of a smaller motor which also contributes to the reduction of manufacturing costs and the reduction of weight. With the desired type of motor employed in the pump, the speed of the pump can be varied to obtain different performance levels and a single pump may be employed to obtain a wide range of operating levels instead of adding stages or changing motors as was required with prior art deep well submersible pumps.